Memory Refreshing System

1. A memory refreshing system, for a memory system including a plurality of memory banks, comprising: (a) memory refreshing means, provided in each of the memory banks, for performing a refresh operation within a corresponding memory bank in response to a refresh request; (b) first memory refresh control means for supplying a refresh request to the memory system every first time period (P 1 ); (c) memory access monitoring means, provided for each of the memory banks, for detecting an access to the corresponding memory bank; (d) a timer, provided for each of the memory banks, for generating a timer output when a first predetermined time (T 1 ), has elapsed since a last access to the corresponding memory bank, and cancelling a counted timer value in response to a next access to the corresponding memory bank; (e) second memory refresh control means, provided for each of the memory banks, for supplying a refresh request to the corresponding memory bank after the first predetermined time (T 1 ) that is longer than the first time period (P 1 ); and (f) a selector, provided for each of the memory banks, for selecting one of the refresh requests from the first and the second memory refresh control means in accordance with the timer output, wherein said system dynamically executes a self-refresh operation and whereby power consumption of a computer operating in a normal mode of operation is reduced by said system.